An unsolved problem in a multi-component system is the dissemination of data that defines changes to system/component states, settings, or configurations to other interrelated systems/components. In a modularized system consisting of independently developed components, it is not feasible for each system that changes information to know the systems that must react to the change. It is also not efficient for each system to frequently check to see if a change has occurred.
Some systems address this problem by creating a network of subscriptions in which a component that changes information maintains a list components needing notification of a change, but this suffers from the problem that the system that changes information must be identified by those system needing notification, and that the critical information must be identified a-priori.
A more general approach is to identify all critical data within a system, and for any component changing such data to send a notification message, perhaps through a dispatch service. This approach also requires that the critical information be identified in advance, and requires that each component changing such data send notification. A common programming error is to change critical data and not cause such notification.
Although details vary with each implementation, this summarizes the current known techniques for dissemination of such information within such systems.